大黄鱼早期发育阶段对盐度的适应性

在5、10、25、40及45这5种盐度梯度下,对大黄鱼初孵仔鱼、开口仔鱼、卵黄囊消失仔鱼、油球消失仔鱼、稚鱼和30日龄幼鱼的耐盐性进行了比较研究,对不同发育时期的死亡率、半数死亡时间、平均死亡时间及72 h半致死盐度等耐盐指标进行了分析。实验结果显示,大黄鱼早期各发育阶段对盐度的适应范围为:30日龄幼鱼为5.5～41.0,卵黄囊消失仔鱼为6.8～23.3,开口仔鱼为8.2～39.4,稚鱼为9.3～26.7,初孵仔鱼为18.9～33.1。表明30日龄幼鱼具有较强的耐盐性,尤其能在较低盐度(5.5)的环境中生活,为大黄鱼的淡化养殖及白点病的淡水浴治疗提供了依据。在正常海水盐度和不投饵状态下,各发育阶段的半数死亡时间,即饥饿不可逆点为:初孵仔鱼(8.6 d)>开口仔鱼(6.5 d)>30日龄幼鱼(5.5 d)>卵黄囊消失仔鱼(4.6 d)>稚鱼(4.0 d)>油球消失仔鱼(1.8 d)。此结果说明在仔鱼开口后应加强外源性营养的投喂,将有助于提高幼体对低盐度的耐受性及其成活率。研究亮点:国内外首次对大黄鱼早期不同发育阶段的耐盐性进行了系统性分析。运用各种耐盐指标测试了大黄鱼鱼苗早期各发育阶段的耐盐性,采用不同方法测定了大黄鱼初孵仔鱼的存活系数,为大黄鱼早期生活环境的选择以及饵料的投喂奠定了基础。

Salinity tolerance of Pseudosciaena crocea during early development

The salinity tolerance of Pseudosciaena crocea during early development(newly-hatched larvae,mouth-opened larvae,yolk-sac disappeared larvae,oil globules disappeared larvae,fry and 30-day-old juvenile) was examined at salinites of 5,10,25,40 and 45.The mortality,mean death time(MDT),median death time(DT50),and median lethal salinity-72 h(MLS-72) were employed as indicators of salinity tolerance.The results showed that suitable salinity for 30-day-old juvenile,yolk-sac disappeared larvae,mouth-opened larvae,fry,and newly-hatched larvae ranged from 5.5 to 41.0,6.8 to 23.3,8.2 to 39.4,9.3 to 26.7,18.9 to 33.1,respectively.Therefore,the salinity tolerance of 30-day-old juvenile of P.crocea is rather strong,especially it can tolerate low-salinity of 5.5.The results lay a theoretical foundation for desalting culture and the fresh water treatment for white spot disease of P.crocea.In normal seawater,the median death time(the point-of-no-return,PNR) at different developmental stages without feeding was determined as follows: newly-hatched larvae(8.6 d) > mouth-opened larvae(6.5 d) > 30-day-old juvenile(5.5 d) > yolk-sac disappeared larvae(4.6 d) > fry(4.0 d) > oil globules disappeared larvae(1.8 d).These indicate that the feeding of exogenous nutrients should be enhanced before the oil globules disappeared,was it will help to improve low-salinity tolerance and survival of P.crocea’s larvae.